Hyperglycemia or elevated NEFA levels can induce insulin resistance in non-diabetic subjects. Determine whether the effect of elevated NEFA levels is rapidly reversible when NEFA levels are allowed to fall to normal. Hyperglycemia leads to a decrease in IR kinase activity in skeletal muscle. Hyperglycemia decreases IR tyrosine kinase activity through enhanced serine (or threonine) phosphorylation of the IR probably mediated via increased PKC activity.